Electron discharge device wherein electromagnetic waves along the slow wave structure have components transverse to the electron beam and deflect out-of-phase electrons from the beam



March 7, 1967 J. M OSEPCHUK ELECTRON DISCHARGE DEVICE WHEREINELECTROMAGNETIC WAVES ALONG THE SLOW WAVE STRUCTURE HAVE COMPONENTSTRANSVERSE TO THE ELECTRON BEAM AND DEFLECT OUT-OF-PHASE ELECTRONS FROMTHE BEAM 2 Sheeiis-Sheet 1 Filed May 27, 19s;

POWER SUPPLY FIG?) FIG.6

INVENTOR. JOHN M OSEPCHUK March 7, 1967 J. M. OSEPCHUK 3,308,331

ELECTRON DISCHARGE DEVICE WHEREIN ELECTROMAGNETIC WAVES ALONG THE SLOWWAVE STRUCTURE HAVE COMPONENTS TRANSVERSE TO THE ELECTRON BEAM ANDDEFLECT OUT-OF-PHASE ELECTRONS FROM THE BEAM Filed May 27, 1963 2Sheets-Sheet 2 F X 4 Z 3; l I L 2x;

INVENTOR. JOHN M. OSEPCHUK AGE/VT 3,308,331 ELECTRON DISCHARGE DEVICEWHEREIN ELECTROMAGNETIC WAVES ALONG THE SLOW WAVE STRUCTURE HAVE COMPO-NENTS TRANSVERSE TO THE ELECTRON BEAM AND DEFLECT OUT-OF-PHASE ELEC-TRONS FROM THE BEAM John M. Osepchuk, Lexington, Mass, assignor toRaytheon Company, Lexington, Mass, a corporation of Delaware Filed May27, 1963, Ser. No. 283,443 6 Claims. (Cl. 3153.6)

This invention relates to crossed-field type electron discharge deviceswherein electrons are compelled by transverse electric and magneticfields to move in energy exchanging relationship with electromagneticwaves, and more particularly to such a device wherein electrons inunfavorable phase relative to the wave are removed from the regionwherein the interaction occurs.

Heretofore, electron sorting has been accomplished in crossed-fieldtraveling wave tubes to remove electrons which are in an unfavorablephase relative to the fields of waves conducted adjacent the electronsso that these electrons in unfavorable phase do not exchange energy withthe wave. Generally, the sorting of electrons takes place byaccelerating the electrons parallel to the electron drift velocity whichis in turn transverse to the crossed electric and magnetic fields whichcompel the drift velocity. One scheme for accomplishing this type ofsorting is disclosed in my United States Patent 3,073,991 which issuedJanuary 15, 1963. The patent described structure in which waves areconducted by a slow wave conducting structure coextensive with anelongated interaction spa-ce. Electrons are injected into theinteraction space at one end and compelled to drift to the other end ofthe space by transverse D.C. electric and magnetic fields. Electronswhich are in favorable phase relative to the fields of the wavesimmediately adjacent the electrons will give up energy to the wave anddecelerate and will move to higher and higher equipotential levels. Ifthe DC. electric field runs toward the wave conducting structure, thenthese electrons will drift closer to the wave conducting structure andwill couple more tightly with the fields of waves conducted by thestructure. On the other hand, electrons in an unfavorable phase relativeto the wave will accelerate and extract energy from the wave and, as aresult, will move to lower equipotential levels and, thus, they willmove away from the wave conducting structure and will eventually becollected by another electrode called the sole electrode which iscoextensive with the wave conducting structure and combines with thestructure to bound the DC. electric field. As the electrons gain or giveup energy to the wave, depending upon whether they are in unfavorable orfavorable phase relative to the wave, they will he accelerated ordecelerated in a direction parallel to the drift velocity of theelectrons and parallel to the flow of wave power. This causes theelectrons to bunch and form favorable bunches or unfavorable bunches.The favorable bunches will continue to exchange energy with the waves,and the unfavorable bunches will be removed from the interaction regionand collected by the sole electrode. Thus, it may be said that thesorting process takes place parallel to the electron drift velocity.

Effective sorting of the above type takes place along a considerablelength of the slow wave structure, and as a result, the electrons inunfavorable phase interact along a considerable length of the structureand, thus, interfere with efficient operation of the device. One objectof the present invention is toaccomplish phase sorting in a shorterlength of the slow wave structure than in the United States Office 3,38,331 fiatented Mar. 7, 1967 past so that the electrons in unfavorablephase are removed from the interaction region after travel through onlya relatively short portion of the interaction space.

It is a feature of the present invention to accomplish phase sorting ina crossed-field traveling wave tube in more than one direction at atime, and more particularly in at least two orthogonal directions sothat electrons in unfavorable phase are more quickly removed from theinteraction region and travel in energy exchanging relationship withwaves conducted by the slow wave structure along only a relatively smallportion of the interaction space. Specific embodiments of the inventioninclude interdigital type slow wave structure formed so that thefringing fields of waves conducted by the structure along portions ofthe interaction space have components transverse to the generaldirection of electron drift through the interaction space and, thus,transverse to the length of the interaction space. More particularly,the interdigital slow wave structure is constructed so that thetransverse component exists along opposite edges of the interactionspace but is substantially nonexistent along the center of theinteraction space. Thus, electrons moving along the edge of theinteraction space which are in unfavorable phase are caused to movefurther from the center of the interaction space and are eventualiycollected by suitable electron collecting structure, whereas electronsalong the edge in favorable phase are caused to move toward the centerand form a tighter beam of electrons along the center of the space.

Other features and objects of the invention will be apparent from thefollowing specific description taken in conjunction with the drawings inwhich:

FIG. 1 illustrates a plan-sectional view of a crossedfield travelingwave tube showing a section of an interdigital delay line along whichthe transverse sorting occurs;

FIG. 2 is a side-sectional view of the same tube shown in FIG. 1 toillustrate components of the tube;

FIG. 3 is a front-sectional view illustrating the flow of unfavorableelectrons transverse to the drift direction of the beam to electroncollecting structure;

FIG. 4 illustrates the high frequncy wave field structure and electronflow to illustrate conventional sorting along the drift path of theelectron beam, as determined by favorable and unfavorable relative phaseareas;

FIG. 5 is a plan view showing favorable and unfavorable phase areas ofan interdigital delay line incorporating features of the presentinvention to illustrate transverse soiging and removal of electrons inunfavorable phase; an

FIG. 6 is a front-sectional view similar to the view in FIG. 3 showinganother embodiment of the invention including another structure forcollecting the unfavorable electrons sorted in the transverse direction.

Turning first to FIG. 1 there is shown a plan-sectional view of acrossed-field traveling wave tube incorporating features of theinvention. The view illustrates the interdigital delay line structurewhereby sorting is accomplished not only in a direction parallel to theelectron beam but in a direction transverse to the beam. The tubeincludes an envelope 1 enclosing an interdigital delay line 2, a soleelectrode 2 coextensive with the delay line defining an interactionspace 4 therebetween and a cathode structure at one end of theinteraction space. The cathode structure includes an electron emittingsurface 5 at the end of a support 6 which encloses a heating element.Opposite the cathode structure 5 is an accelerating electrode 7 foraccelerating electrons emitted from the cathode to an initial totalvelocity at which the electrons are injected into the interaction space.A transverse magnetic field B between the poles 8 and 9 of a magnetcompel electrons issuing from the cathode to follow arcuate paths andthus enter the interaction space. Thereafter, the electrons proceedthrough the interaction space as a beam 11 and generally followcycloidal or epicycloidal paths under the influence of transverseelectric and magnetic fields E and B. The transverse electric field runsfrom the slow wave structure 2 to the sole electrode 3. The structure 2preferably is at the same potential as the envelope which is groundpotential, and so the electric field E is created by applying a negativepotential from a power supply 12 to the sole electrode 3.

In forward wave operatoin, where wave power flows in the same directionas the electron beam, radio frequency waves are conducted to the slowwave structure 2 by the coaxial transmission line 13, and these wavesafter interacting with the electrons in the beam 11 are conducted fromthe slow wave structure 2 by another coaxial transmission line 14. Thefields of the waves extend into the interaction space 4 in the mannershown in FIG. 4 so that the electrons in the beam 11 interact with thesefields and exchange energy with the fields. In backward waveinteraction, the wave power flows in a direction opposite the beamdirection; however, the phenomenon involved in the exchange of energybetween the waves and the electrons is substantially the same as inforward wave interaction.

FIG. 4 illustrates the fringing fields of the waves in the interactionspace 4 between the delay line 2 and sole electrode 3. The electron beam11 in FIG. 4 is shown directed from left to right, and the direction ofthe fringing fields is shown for one instantaneous condition. Thevertical broken lines represent the areas along the beam where theelectrons are instantaneously in favorable or unfavorable phase relativeto the instantaneous wave fields. Favorable phase areas denoted F existswhere the instantaneous fields are directed substantially in the samedirection as the electron beam, and unfavorable regions denoted U existwhere the fields are directed opposite to the direction of the beam. Asa result, the electrons located at areas of instantaneous favorablephase give up energy to the fields and move to higher equipotentiallines as illustrated by the broken arrows 15. Thus, these electrons movetoward the wave structure 2. In areas of unfavorable phase, on the otherhand, the electrons gain energy from the fields and move to lowerequipotential lines as illustrated by the broken arrows 18. This actioncauses the electrons to bunch and to form an undulating chargeconcentration of electrons moving adjacent the delay line. This phasefocusing action brings the undulations into favorable phase with respectto the wave fields so that there is an efiicient exchange of energybetween the electrons and the waves.

Electron storing is a similar but different phenomenon and serves toremove from the beam electrons which are not properly phase focused.Electron sorting as accomplished in my above-mentioned patent is due toelectron motion transverse to the beam in the XY plane as shown in FIG.4. It is one object of the present invention to also accomplish thistype of electron sorting in at least one other plane such as the YZplane, for example, with electron motion in the Z direction so thatsorting occurs in more than one plane and is substantially completedalong a relatively short section of the wave conducting structure 2.

The transverse sorting in the Z direction is accomplished by forming thetortuous path provided by the interdigital delay line or any other typeof delay line with portions that conduct the RF waves so that theelectric fields of the waves have a component in the Z direction. Thisis shown by the section of the wave structure 21 in FIG. 1 wherein thebase 22 and end 23 of a number of the fingers which form this section ofthe structure are at an angle other than 90 to the direction of thebeam, whereas the center portions of the fingers are disposed at a 90angle to the beam. It is preferred that the structure be formed so thatthe fringing wave fields 4 have a component transverse to the beam alongthe edges of the interaction space rather than along the center of theinteraction space so that the transverse sorting will be accomplishedalong the edges where it is most effective.

The interdigital delay line construction 21 as shown in FIG. 1 is merelyone example of a suitable structure whereby the wave fields have acomponent transverse to the direction of the beam so that transversesorting is accomplished. Other structures whereby this transversecomponent is produced are apparent to those skilled inthe art and willalso accomplish the transverse sorting.

FIG. 5 is a plan view showing the areas of instantaneous favorable andunfavorable phase (F and U) for the section of delay line 21 as viewedin the YZ plane. The phase areas are shown by broken lines similar tothe lines in FIG. 4 and represent an edge view in the YZ plane of phaseareas similar to those designated F and U in FIG. 4. As shown in FIG. 5,the phase areas have substantially the same shape as the fingers in thesection 21 of delay line 2. The solid-line arrows 32 extending fromunfavorable phase area, denoted U, represent the instantaneous directionof wave fields in the ZY plane, just as the solid vectors in FIG. 4represent the instantaneous direction of RF fields in the XY plane.Along opposite edges of the interaction space, the fields in thevicinity of an unfavorable phase area, denoted U, obviously havecomponents such as 34 and 35 directed toward the beam 11, while thefields 3a in the vicinity of favorable phase area, denoted F, have acomponent such as 37 and 38 directed away from the center of the beam.The components 34 and 35 will cause electrons to disperse from the beamas indicated by broken arrows 41 and move transverse to the direction ofthe beam. No such action will occur in the vicinity of a favorable phasearea, and, in fact, the beam will become tighter and dispersed electronswill be driven back into the center of the beam in this plane. Thus,electron sorting is accomplished in the Z direction as well as in the Ydirection, and unfavorable electrons are removed quite rapidly from thebeam, and the undulations of the beam become quickly synchronized and inphase with the fields of the waves so that efficient operation results.

FIG. 6 is a front-sectional view of the tube already described withreference to FIGS. 13 and shows an alternate structure including twoadditional electrodes within the envelope disposed coextensive with andadjacent the edges of the sole electrode for collecting the electronssorted in the transverse or Z direction. These additional electrodes 51and 52 are mounted on insulating bases 54 and 55, respectively, andleads 56 are provided coupling these electrodes to the power supply 12.The sole electrode 57 in the embodiment shown in FIG. 6 is preferably afiat plate without the end shields 3a and 3b shown in the embodiment ofFIG. 3. Furthermore, it is generally preferred that the electrodes 51and 52 be at the same DC. potential which is preferably somewhat greaterthan cathode potential so that the transverse sorting action will resultin a more rapid removal of unfavorable electrons. The end shields willact as retaining boundaries on the properly focused and phased beamelectrons. The potentials on the additional electrodes 51 and 52 arepreferably adjusted for an optimum combination of transverse electronsorting and beam containment.

The above descriptions with reference to structure in FIGS. 16 relate towhat is sometimes called a positiveline crossed-field tube because thedelay line or wave conducting structure 2 is positive with respect tothe coextensive sole electrode 3. Principles of the invention arereadily applicable to the negative line tube where the Wave conductingstructure is negative relative to the sole electrode. Electron sortingof the type described in my Patent 3,073,991 employed in a negative linetube would result in the flow of unfavorably phased electrons alongpaths similar to paths 18 in FIG. 4 but toward the delay line. However,transverse sorting illustrated in FIG. 5 would occur substantially asdescribed herein.

This concludes descriptions of specific embodiments of the presentinvention wherein electrons are sorted and removed from a beam dependingupon whether the electrons are in favorable or unfavorable phaserelative to the fields of high frequency waves conducted by structureadjacent the beam, this sorting being accomplished in a directiontransverse to the direction of the beam by the action of fieldcomponents of the waves directed transverse to the beam. The specificembodiments include an interdigital delay line for conducting the waveadjacent the beam, the serpentine passage formed by the delay lineincluding portions which conduct the wave along paths at an acute angleto the direction of the beam. However, these embodiments are describedby way of example and do not limit the spirit and scope of the inventionas set forth in the accompanying claims.

What is claimed is: 1. An electron discharge device comprising: a sourceof electrons; means producing mutually perpendicular D.C. electric andmagnetic fields for compelling said electrons to move as a beam throughan interaction space; and a slow wave structure for conductingelectromagnetic waves adjacent said interaction space so that I theelectric fields of said waves along opposing edges of said interactionspace form oblique angles with and have a component transverse to thedirection of said beam and parallel to said magnetic field; wherebyfavorably phased electrons along the edges of the interaction space arecaused to move toward the center of the beam and unfavorably phasedelectrons are caused to move away from the center of said beam. 2. Anelectron discharge device comprising: a source of electrons; aninteraction space; means producing mutually perpendicular D.C. electricand magnetic fields for compelling said electrons to move through saidinteraction space as a beam; and a wave conducting structure adjacentsaid interaction space, at least a portion of which conducts radiofrequency waves along paths adjacent to opposing edges of saidinteraction space defining oblique angles with respect to the directionof movement of said beam and along a path parallel to said magneticfield adjacent to the center of said beam. 3. An electron dischargedevice comprising: a source of electrons; an elongated interaction spaceadjacent said source of electrons; means for injecting said electronsinto said interaction space; means for producing transverse D.C.electric and magnetic fields in said interaction space for compellingsaid electrons to move through said space as a beam; and a waveconducting structure adjacent said interaction space for conductingwaves in synchronism with said electrons whereby there is an exchange ofenergy between said electrons and said waves, and the radio frequencyfields of said Waves in said space along opposing edges of saidinteraction space defining oblique angles with respect to said beam andhaving a component parallel to said magnetic field. 4. An electrondischarge device comprising:

a source of electrons; an elongated interaction space adjacent saidsource of electrons; means for injecting said electrons into saidinteraction space; means for producing transverse D.C. electric andmagnetic fields in said interaction space for compelling said electronsto move through said space as a beam;

action space for conducting waves in synchronism with said electronswhereby there is an exchange of energy between said electrons and saidwaves, said structure including portions having a single surfaceparallel to the magnetic field and perpendicular to the DC. electricfield together with two additional surfaces extending therefrom andforming oblique angles with respect to said magnetic field so that theradio frequency fields of said waves have a substantial componenttransverse to said beam.

5. An electron discharge device comprising:

a source of electrons;

an elongated interaction space adjacent said source of electrons;

means for injecting said electrons into said interaction space;

means for producing transverse D.C. electric and magnetic fields in saidinteraction space for compelling said electrons to move through saidspace as a beam;

and a wave conducting structure adjacent said interaction space forconducting waves in synchronism with said electrons whereby there is anexchange of energy between said electrons and said waves, said structureincluding portions adjacent to the electron injection means having asingle surface parallel to the magnetic field and perpendicular to theDC. electric field together with two additional surfaces extendingtherefrom and forming oblique angles with respect to said magnetic fieldso that the radio frequency fields of said waves along opposing edges ofsaid interaction space have a substantial component transverse to saidbeam for compelling electrons which are in an unfavorable phase relativeto said wave fields to move away from the center of said beam andelectrons which are in a favorable phase relative to said wave fields tomove toward the center of said beam.

6. A crossed-field electron discharge device comprising:

an envelope enclosing a slow wave conducting structure;

an electrode coextensive with said structure defining an interactionspace therebetween;

a source of electrons at one end of said interaction space;

means for producing transverse D.C. electric and magnetic fields in saidinteraction space for compelling electrons from said source to move as abeam through said space in a direction substantially transverse to bothsaid fields;

said wave conducting structure including portions adjacent to theelectron source having a single surface parallel to the magnetic fieldand perpendicular to the DC. electric field together with two additionalsurfaces extending from the ends of said single surface and formingoblique angles with respect to said magnetic field whereby the radiofrequency fields of said waves along opposing edges of said interactionspace have a substantial component transverse to said beam so thatelectrons in an unfavorable phase relative to the fields of said wavesare caused to move away from the center of said beam and electrons infavorable phase are caused to move toward the center of said beam;

and means adjacent to opposing edges of said interaction space forcollecting said unfavorably phased electrons.

References Cited by the Examiner UNITED STATES PATENTS HERMAN KARLSAALBACH, Primary Examiner.

and a wave conducting structure adjacent said inter- R. D. COHN,Assistant Examiner.

1. AN ELECTRON DISCHARGE DEVICE COMPRISING: A SOURCE OF ELECTRONS; MEANSPRODUCING MUTUALLY PERPENDICULAR D.C. ELECTRIC AND MAGNETIC FIELDS FORCOMPELLING SAID ELECTRONS TO MOVE AS A BEAM THROUGH AN INTERACTIONSPACE; AND A SLOW WAVE STRUCTURE FOR CONDUCTING ELECTROMAGNETIC WAVESADJACENT SAID INTERACTION SPACE SO THAT THE ELECTRIC FIELDS OF SAIDWAVES ALONG OPPOSING EDGES OF SAID INTERACTION SPACE FORM OBLIQUE ANDLESWITH AND HAVE A COMPONENT TRANSVERSE TO THE DIRECTION OF SAID BEAM ANDPARALLEL TO SAID MAGNETIC FIELD; WHEREBY FAVORABLY PHASED ELECTRONSALONG THE EDGES OF THE INTERACTION SPACE ARE CAUSED TO MOVE TOWARD THECENTER OF THE BEAM AND UNFAVORABLY PHASED ELECTRONS ARE CAUSED TO MOVEAWAY FROM THE CENTER OF SAID BEAM.